The Doomsday Clock, which has been used to examine the world’s vulnerability to global catastrophe for nearly a century, has moved one second closer to midnight. On Jan. 28, the Bulletin of the Atomic Scientists announced that the Doomsday Clock was set at 89 seconds to midnight,

What is the Doomsday Clock? It's 2025 and scientists have reset the clock closer to midnight and global catastrophe. Here's what it all means.

Artificial intelligence was not listed as a chief concern two years ago, the last time the Bulletin of the Atomic Scientists moved the clock closer to global catastrophe.